A common problem with recording devices such as camcorders and digital cameras is audio noise contamination of the recorded audio signal. As referred herein, audio noise includes unwanted audio signal, such as wind noise or any other undesired audio noise that is present within a particular range of frequency in an audio signal being acquired or recorded. For example, when a camcorder is used to record an outdoor scene, which frequently has wind noise that may contaminate or distort the desired speech, music, and background waterfall sound that are the subjects of the recording. FIG. 1 illustrates a spectrogram 100 of a recording audio signal that contains wind noise. The spectrogram represents the magnitude of the short-time frequency decomposition of the recorded audio signal, with time on the horizontal axis, and frequency on the vertical axis. The light color represents high energy, and the dark color represents low energy. As illustrated, wind noise 110 is known to occur in the lower frequency regions of the spectrum. Wind noise most frequently occurs in outdoor scenes, which typically have other desired background audio signals as well, such as waterfall or rivers as shown by the natural low frequency background 120. The spectrogram 100 also shows the presence of the desired speech signal 130.
Some prior methods for reducing noise employ high-pass filters, sometimes with adaptive cut-offs. However, these high-pass filtering techniques often leave artifacts at the lower frequencies of the recorded audio signal. Consequently, the playback of the recorded audio signal sounds “hollow” because its low-frequency signal portion, which typically includes certain desired background sound, has been removed along with the noise. Other prior methods for reducing noise employs mechanical screens, such as wind screens, that are placed over audio recording mechanisms, such as microphones, of the recording devices. However, the mechanical screens still let through some of the noise.